1. Field of the Invention
This invention relates to a reference voltage generating circuit and more particularly to a reference voltage generating circuit for generating a reference voltage of low level.
2. Description of the Prior Art
When the signal processing system of a radio receiver is formed as an integrated circuit (IC), a reference voltage supply source must be provided within the IC as a bias source for a transistor therein or for comparing or shifting the levels of certain signals relative to the reference voltage. When a radio receiver, which can be operated by, for example, two dry cells of size AA, is considered, the reference voltage therefor becomes about 1 to 1.5 V.
In the prior art, a reference voltage generating circuit is provided with a resistor and a single diode or two diodes connected in series between a power source terminal (input terminal) and the ground and a reference voltage is derived from the connection point between the resistor and the diode or diodes. However, such known reference voltage generating circuit is dependent on the temperature and hence has a poor temperature characteristic. Although a reference voltage generating circuit has been proposed with a good temperature characteristic, such prior art circuit is disadvantageous in that the reference voltage is considerably dependent on the input voltage or its fluctuation.